Voltage regulator indicating circuit for undervoltage, normal voltage and overvoltage conditions

ABSTRACT

An indicating circuit for use in a vehicular electrical system having a DC power source and a dynamoelectric machine to supply a charging current to the DC power source. One or more indicating lamps are provided to give visual indication of the various operating conditions of the dynamoelectric machine to indicate failure of an alternator or regulator components or to indicate below normal, normal, and above normal voltage outputs therefrom. Where two or more indicating lamps are used, they are controlled by voltage differential amplifiers having gated outputs therefrom connected to a third amplifier. The third amplifier control energization of the indicating lamp which indicates the normal voltage output of the dynamoelectric machine, and energization of either of the two voltage differential amplifier circuits will render the third amplifier inoperative by a signal through the associated gate circuit.

United States Patent Riff [451 June 27, 1972 54] VOLTAGE REGULATORINDICATING 3,505,663 4/1970 Yule ..340/248 CIRCUIT FOR UNDERVOLTAGE,2,817,830 12/1957 Raver ..-....340/249 NORMAL VOLTAGE AND 3'33??? 1913222 7 a USIBI' 6t 72 inventor: James A. Riff, Chicago, 111. PrimaryExaminer-Gerard Strecker Attorney-Mueller & Aichele [73] Assignee:Motorola, Inc., Franklin Park, Ill. 22 Filed: Jan. 14, 1970 [57]ABSTRACT An indicating circuit for use in a vehicular electrical system[211 App! L890 having a DC power source and a dynamoelectric machine tosupply a charging current to the DC power source. One or [52] us. Cl...340/248 A, 324/51, 324/133, more in ca ng lamps a e p ovided to gi eisual indication of 340/249 the various operating conditions of thedynamoelectric 51 Int. Cl. ..oon- 19/16, GOlr 31/02, G08b 21 00 machineto indicate failure of an alternator 9r regulator [58] Field of Search..324/51, 725, 133; 340/248, Ponems or to indicate below normal, normal,and above 340 9 mal voltage outputs therefrom. Where two or moreindicating lamps are used, they are controlled by voltage differentialam- [56] References Cited plifiers having gated outputs therefromconnected to a third amplifier. The third amplifier control energizationof the in- UNITED STATES PATENTS dicating lamp which indicates thenormal voltage output of the dynamoelectric machine, and energization ofeither of the two 3,31 1,907 3/1967 Teal voltage differential ampfifiercircuits n render the third 332L754 5/1967 Gnmm et "m34o/249 plifierinoperative by a signal through the associated gate cir- 3,354,448 1H1967 Brolin ..340/248 cuiL 3,437,916 4/1969 Mazurkevics ..340/248 UX3,457,560 7/1969 McKinley ..340/248 7 Claims, 2 Drawing Figures "2 70 1!72 94 N 31 SW 130- n4 96 GROUND IIG PATENTEDJUKZ'! 1972 3. 673 588INVENTOR.

JAMES A. RIFF ATTORNEYS.

VOLTAGE REGULATOR INDICATING CIRCUIT FOR UNDERVOLTAGE, NORMAL VOLTAGEAND OVERVOLTAGE CONDITIONS BACKGROUND OF THE INVENTION This inventionrelates generally to a voltage regulator indicating circuit, and moreparticularly to a voltage regulating indicating circuit which can beused either permanently on a motor vehicle or can be plugged in as atester to ascertain the operating condition of a generator oralternator, or the like.

Most present day vehicles use either a direct current generator or analternator with associated rectifiers to apply current to the batteryand the electrical accessories of the vehicle. The current applied tothe battery serves to recharge the battery and maintain the chargetherein at a given level. In prior electrical systems there is anindicating device, such as a lamp or meter, which has one end connectedto the battery and the other end connected to the output of the voltageregulator. Any difference of potential across the indicating device willgenerally give an indication that the output of the altemator is zero orbelow the desired output level. That is, under some malfunctionconditions of the generator or alternator the indicating device willwarn the operator of the motor vehicle, for example, by energizing alamp as is most often the case. When the indicating lamp is notenergized the operator is led to believe that the electrical system ofhis vehicle is operating properly, a presumption that may lead todisastrous results. This is true because light indications, or for thatmatter meters as well, only indicate certain kinds of malfunctions orfailures. There are some kinds of component or system failures that willopen the current path through the indicating lamp or meter. Since alight off" condition is assumed by the operator to mean all is well"with the electrical system, he will not be aware of this type ofmalfunction. Also, such vehicles are not equipped to indicate a failurethat would apply excessive charge to the battery, as for example, whenthe voltage regulator malfunctions to increase the output voltage of thegenerator or alternator. Additionally, vehicles generally are notequipped with light indicating means to indicate that the batterycharging system of the vehicle is operating properly. Therefore, anoperator of a motor vehicle may drive many miles without ever realizingthat there is something wrong with the battery charging system of thevehicle.

Also, in servicing the electrical system of vehicles to calibrate orrepair the battery charging system, complicated and expensive equipmentis required. It requires a skilled person to evaluate the informationobtained by the testing equipment to determine whether or not thebattery charging system is operating properly, and if not, to determinethe cause of the improper operation and repair the same.

SUMMARY OF THE INVENTION Accordingly, it is an object of this inventionto provide an indicating circuit that will energize an indicating devicesuch as a lamp or the like upon failure in any respect of the system tosupply charging current to the battery of a motor vehicle.

Another object of this invention is to provide a voltage regulatorindicating circuit which indicates the above normal and normal voltageconditions within the battery charging circuit of tee vehicle inaddition to the no charge condition.

Yet another object of this invention is to provide a voltage regulatorindicating circuit which can be used as a test instrument to indicatethe various modes of operation of a battery charging circuit thereby toindicate to an unskilled person the type of malfunction encountered, ifany.

A still further object of this invention is to provide a voltageregulator indicating circuit which is efficient and reliable inoperation, inexpensive to manufacture and which is small in size to beeasily incorporated within the same housing as an associated voltageregulator.

Briefly, in one illustrated embodiment, the voltage regulator indicatingcircuit of this invention can be incorporated directly within the samehousing as a transistorized voltage regulator. In this instance, theindicating circuit receives control voltage only from the output of thegenerator or alternator, whichever the case may be, to render a currentcontrol device non-conductive when a normal voltage output is obtained.However, when no voltage output or a below voltage output is obtainedfrom the generator or alternator, the current control device isautomatically rendered conductive by a current path from the batterythrough an associated indicating lamp. By this arrangement a failure ofthe alternator or voltage regulator which causes an open circuit willstill cause energization of the indicating device.

Where the indicating circuit is used as a test instrument in accordancewith another illustrated embodiment, the current control device has acontrol electrode thereof connected to a pair of resistors which form acommon circuit point therebetween and this circuit is then used toindicate a normal voltage output of the generator or alternator. Gatesignals are applied to the juncture between the resistors in response toeither below normal voltage output or above normal voltage output of thegenerator or alternator to disable the current control device. In thisinstance, the indicating lamp used to indicate a normal voltage currentcondition will be rendered inoperative in response to either of the gatesignals and one or the other indicating lamps will be energized to givean indication of an abnormal voltage condition, i.e., at below normalvoltage condition or an above normal voltage condition.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagramillustrating a voltage regulator circuit incorporating the voltageregulator indicating circuit of this invention; and

FIG. 2 is a schematic diagram illustrating a voltage regulatorindicating circuit of this invention which can be used as a test circuitto indicate the various modes of operation of a generator or alternatorbetween the below normal voltage, normal voltage, and above normalvoltage conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. I there isseen a transistorized voltage regulator circuit designated generally byreference ml meral 10 which most advantageously incorporates anindicating control circuit 12 for controlling energization of a lamp 14,it being understood that any suitable indicating device may be used. Thelamp 14 has one end thereof connected to a terminal 16 which, in turn,is connected preferably to the ignition switch, not shown, of anautomobile to receive energizing current therefrom when the ignitionswitch is closed and before the engine has started running to indicatethat no voltage output is provided by the alternator or generator of thevehicle.

The voltage regulator circuit 10 receives energizing current through areed switch 18 which is actuated by an electromagnetic device 20 havingone end thereof connected to ground potential via a line 22 and theother end thereof connected to a terminal 24 through a resistor 26. Theterminal 24 is arranged for connection to the ignition switch of theautomobile to initially cause closing of the reed switch 18 to energizethe regulator circuit 10 only when the ignition switch is in the onposition. A capacitor 28 is connected across the electromagnetic device20, and an isolating diode 30 has one end thereof connected to thejuncture of the electromagnetic device 20 and capacitor 28 and the otherend thereof connected to a terminal 32 for receiving the output voltagefrom a generator or alternator, whichever the case may be, which alsoserves to energize the electromagnetic device 20. Also, the regulator 10is provided with a terminal 34 arranged for connection to the battery ofan automobile.

A power transistor 36, here shown as a PNP type, has its collectorelectrode connected to a terminal 38 and its emitter electrode connectedthrough a resistor 40 to the positive potential applied to terminal 34.Also connected to the collector electrode of transistor 36 is a diode 37which may serve as a protection device. When the voltage regulatorcircuit 10 is used to regulate the output voltage of an alternator, theterminal 38 is connected to a field winding 42 within the altematorbody, not shown, in a common and well-known manner.

The base control voltage for transistor 36 is established by theemitter-collector electrode current path of a PNP control transistor 44and a bias resistor 46. The resistor 46 and transistor 44 together withthe resistor 40 form a variable value voltage divider network to controlthe conduction of transistor 36 in accordance with the output voltagevariation applied to terminal 32 to regulate the output of an alternatorby correspondingly varying the current applied to the field winding 42thereof through terminal 38. The value of resistor 46 is relatively highand, as such, the bulk of the current through the circuit will be in thefield winding 42.

A voltage divider network including a plurality of series connectedresistors 48, 50 and 52 are connected between the reed switch 18 and theterminal 34 and are selected to provide a voltage value at circuit point54 of proper potential for operation of the voltage regulator circuit10. Preferably, a temperature responsive variable resistor 56 isconnected in parallel with a resistor 48 and is selected to effectivelytrack changing voltage requirements of a battery being charged atdifferent temperatures. That is, the temperature responsive variableresistor 56 compensates for variation in ambient temperature to insureproper charging current to a battery.

A reference voltage device 58, preferably a zener diode, has the'anodethereof connected to the circuit point 54 and the cathode thereofconnected to the base electrode of the transistor 44, a resistor 60 anda resistor 62. The resistance value of the resistors 48 and 60 togetherwith the resistance value of the temperature responsive device 56 areselected,

together with the breakover voltage value of the reference voltagedevice 58, to cause conduction of the reference voltage device 58 at apredetermined voltage value which, in turn, controls the output currentfrom power transistor 36 to apply energizing current to the terminal 38.This energizing current, in the case where the voltage regulator circuit10 is used to supply energizing current to the field winding 42 whichmay be a pulsing current having a frequency in the order of 3,000 Hzmore or less.

A filter capacitor 64 is connected between the terminal 34, whichreceives battery potential, and the ground potential to provide afiltered operating potential across the load electrodes of transistors36 and 44 while pulses of DC current are supplied to the field winding42. Also, a diode 63 is added to the circuit to serve as a transientsuppressor for negative pulses.

In accordance with this invention, the indicating circuit 12 includes acurrent control device 65,- preferably being a transistor which has-itsemitter electrode connected to the indicating lamp l4 and its collectorelectrode connected to ground potential. The base electrode oftransistor 65 is connected to a parallel network comprising a resistor66 and a capacitor 67 and a blocking diode 68. The blocking diode 68 hasits anode connected to the terminal 32 to receive a potential only fromthe output of an alternator to control de-energization of the lamp 14 inresponse thereto.

In operation, the transistor 65 is rendered conductive'by current flowfrom the battery through the indicating lamp 14, the emitter basejunction of the transistor and the resistor 66. This current flow isobtained by the positive potential applied to the ignition switch of theautomobile. Therefore, under the initial starting sequence condition ofan engine, when the switch is turned on and the engine is not running,transistor 65 is rendered highly conductive to energize the lamp 14,which may be red or have a red lens, thereby giving an indication thatno voltage output is developed by the alternator. However, once-theengine has started, a voltage is applied to the capacitor 67 through theblocking diode 68 in response to the output of the alternator as sensedon the terminal 32. The charge on capacitor 67 increases to the value ofthe output of the alternator which, in turn, reverse biases the baseemitter junction of transistor 65 to render it non-conductive andextinguish the indicating lamp 14. When the voltage value at the outputof the alternator drops below a certain value the capacitor 67 willdischarge somewhat through the parallel resistor 66 to reduce thevoltage applied to the base electrode of transistor 65. This action willprovide a slight forward bias on transistor 65 and it will conduct to adegree-depending upon the amount of forward bias. Therefore, when theoutput of the alternator is only slightly below the required value thelamp 14 will glow slightly and when the output of the alternator issubstantially below the required value the lamp 14 will glow brightly,and all conditions between these two extremes will cause a correspondingchange in lamp brightness.

The indicating circuit 12 is so small and requires so few componentsthat it can readily fit within the same housingas the voltage regulatorcircuit 10 to simplify the-electrical wiring, as generally accomplishedby wire harnesses, of a motor vehicle.

The novel advantages obtained by using the indicating circuit 12 makespossible the construction of a simple, inexpensive test circuit whichcan be used to analyze the various voltage conditions at the output ofan alternator and which can be portable or made part of the motorvehicle. FIG. 2 illustrates one embodiment of a test circuit constructedin accordance with the principles of this invention. Here, the testcircuit is designated by reference numeral 70 and is provided with aplug 72 to mate with a corresponding receptacle provided on the vehicle,not shown. The test circuit 70 is very compact and relativelyinexpensive and, as Such, can be made part of a permanent installationin a vehicle for. continuous monitoring of the alternator output.

To accomplish this, an indicating lamp 74 is connected to a firstvoltage value responsive circuit 76 to be energized therefrom inresponse to a voltage value condition from the alternator which is belowthe normal voltage value. A second lamp 78 is connected to a secondvoltage value responsive circuit 80 to be energized therefrom inresponse to a voltage value condition from an alternator which is abovethe normal voltage value. The output signals from each of the voltagevalue responsive circuits 76 and 80 are coupled through gating diodes 82and 84, respectively, to disable a transistor stage 86, which whenconducting energizesan indicating lamp 88 to indicate the normal voltagevalue condition of the alternator.

The voltage value responsive circuits 76 and 80 are here illustrated asbeing substantially the same as the voltage regulator 10 shown inFIG. 1. That is, the voltage value responsive circuit 76 includes apower transistor 90 having the collector electrode thereof connected inseries with the indicating lamp 74 and the emitter electrode thereofconnected to a line92 which, in turn, is connected to a plug connector94 of the plug 72. A control transistor 96 is connected in series with aresistor 98 and the juncture therebetween is connected to the baseelectrode of the power transistor 90.A pair of resistors 100 and 102 areconnected to the base electrode of transistor 96 and to the cathode of areference voltage device 104, preferably a zener diode, or the like.

In this embodiment, the voltage value responsive circuit 76 isadjustable by means of a voltage divider network including a resistor106 and a potentiometer 108 connected in series therewith, it beingunderstood that the potentiometer 108 may be a fixed valve resistor, ifdesired. Therefore, the maximum voltage value of the below voltagecondition will be determined by the value of potentiometer 108 which, inturn, determines the breakover voltage point of zener diode 104 torender transistor 90 non-conductive and extinguish the indicating lamp74. The voltage divider network comprising resistor 106 andpotentiometer 108 receives its operating potential from a plug connector110 of a plug 72 through a diode 1 12 connected in series therewith.Also, a filter capacitor 1 14 is connected between the plug connector94, which receives DC potential from the ignition switch of the vehicleand to the plug connector 116 'of the plug 72 which is connected toground potential. Connected in parallel with capacitor 114 is a diode118 for suppressing undesirable transients.

Operating potential from plug connector 110 is also delivered to aresistor 1 19 and a potentiometer 120 associated with the voltage valueresponsive circuit 80. A filter capacitor 121 is connected between theresistor 119 and potentiometer 120. Here also, the potentiometer 120 maybe a fixed value resistor if desired. The resistance value of thepotenfiometer 120 will determine the minimum voltage at which theabnormally high voltage value condition will be indicated by theindicating lamp 78. That is, the voltage value which will causeconduction of a zener diode 122 is adjustably selected by thepotentiometer 120. A power transistor 124 is connected in series withthe indicating lamp 78 and is controlled in response to a controltransistor 126 connected to the base electrode thereof. However, in thisinstance a resistor 128 is connected in series with the transistor 126and the base electrode of transistor 124 to limit conduction oftransistor 124 within prescribed values since this circuit operates athigher voltage values and current. Also, a resistor 130 is connected tothe juncture between the base electrode of transistor 126 and the anodeof zener diode 122, and a resistor 132 is also connected to thisjuncture.

Preferably, the resistance values of the voltage value responsivecircuit 76 are selected to cause the reference voltage device 104thereof to be activated at, for example, a value of 13.2 volts, more orless, at the output of the alternator to render transistor 90non-conductive and extinguish the low voltage value condition indicatinglamp 74. On the other hand, the reference voltage device 122, which isconnected in opposite conductive polarity in the circuit than that ofthe reference voltage device 104, will be activated upon sensing anoutput at the alternator in excess of 14.9 volts, more or less.

In accordance with this embodiment of the invention the gating diodes 82and 84 have their cathodes connected to a common circuit point 134located between a pair of series connected resistors 136 and 138connected in the base circuit of a transistor 140 of the energizingcircuit 86. The emitter electrode of the transistor 140 receives apositive potential from the plug connector 94 via a line 141 and thecollector electrode of transistor 140 is connected to ground potentialthrough a current limiting resistor 142 and the indicating lamp 88.

With a normal voltage value output at the alternator, both voltage valueresponsive circuits 76 and 80 are inoperative and, as such, no gatingsignal is applied through either of the gating diodes 82 or 84. Thisaction will cause normal forward bias potential to be applied totransistor 140 to render it conductive and energize the indicating lamp88 which, in turn, will indicate that a normal voltage value conditionexists at the output of the alternator. However, should either of thecircuits 76 or 80 become energized in response to their correspondingabnormal voltage value condition at the output of the altemator, agating signal will be applied through the corresponding diode 82 or 84to apply a positive potential to a base of transistor 140 therebyrendering it non-conductive to extinguish the indicating lamp 88. Theplug connectors 94 and 1 may be jumpered together by internal orexternal circuit means when the circuit 70 of FIG. 2 is used as aportable tester.

If desired, the indicating lamps 74 and 78 may be red while theindicating lamp 88 may be green. However, it will be understood that anysuitable combination of colors or indicia can be displayed by the lamps74, 78 and 88. Accordingly, the regulator indicating circuit of thisinvention provides a novel means for readily obtaining information as tothe several conditions of operation of a charging circuit in a vehicle,for giving visual indication of the several possible conditions of avoltage regulator circuit and for use as a test instrument which iseasily portable.

I claim:

1. A voltage regulator indicating circuit for use in a vehicular systemwhich has a DC power source and a dynamoelectric machine for supplyingcharging current to the DC power source, comprising in combination:first and second indicators, voltage value responsive circuit meanshaving first and second inputs, said first input being coupled to the DCpower source and said second input to the output of said dynamoelectricmachine, said voltage value responsive circuit means comparing saidinputs and being coupled to said first indicator to energize the samewith said first and second inputs being substantially unequal, aswitching circuit coupled in circuit with the DC power supply, saidvoltage value responsive circuit means and said second indicator, saidswitching circuit energizing said second indicator with said voltages ofsaid first and second inputs of said voltage value circuit means beingsubstantially equal, and said switching circuit further being disabledwith said first and second inputs of said voltage value responsivecircuit means being substantially unequal.

2. The voltage regulator indicating circuit according to claim 1including said voltage value responsive circuit energizing said firstindicator over a first predetermined range of voltage differencesbetween said first and second input voltages, a third indicator, secondvoltage value responsive circuit means having a first and second inputand an output, said first input being coupled to the DC power source andsecond input being coupled to said dynamoelectric machine, said secondvoltage value responsive circuit comparing said first and second inputsthereof and being coupled to said third indicator to energize the samein response to said inputs being substantially unequal over a secondpredetermined range of voltage differences, said first and secondvoltage ranges being different, said second voltage value responsivecircuit further being coupled to said switching circuit to disable thesame over said second range of voltage difierences.

3. A voltage regulator indicating circuit to be connected to a batterycharging circuit within an electrical system of a motor vehicle toindicate the operating conditions of the dynamoelectric machine used tocharge the battery, comprising:

a first voltage differential amplifier circuit having a first currentcontrol device which has a pair of load electrodes and a controlelectrode;

a first indicating lamp connected in circuit with the load electrodes ofsaid first current control device to be energized in response toconduction thereof;

a first reference voltage means coupled to said control electrode ofsaid first current control device, said first reference voltage meansarranged for connection to the battery charging circuit within theelectrical system of the motor vehicle, said first reference voltagemeans being rendered operative in response to a first abnormal voltageoutput condition of the dynamoelectric machine within the electricalsystem of the motor vehicle,

a second voltage differential amplifier circuit having a second currentcontrol device which has a pair of load electrodes and a controlelectrode;

a second indicating lamp connected in circuit with the load electrodesof said second current control device to be energized in response to theconduction thereof;

a second reference voltage means coupled to said control electrode ofsaid second current control device, said second reference voltage meansarranged for connection to the battery charging circuit within theelectrical system of the motor vehicle, said second reference voltagemeans being rendered operative in response to a second abnormal voltagecondition at the output of the dynamoelectric machine within theelectrical system of the motor vehicle;

- a switching circuit including a third current control device havingload electrodes and a control electrode, a third indicating lampconnected in circuit with the load electrodes of said third currentcontrol device to be energized in response to the conduction thereof toindicate a normal voltage condition of the electrical system;

resistance means connected to the control electrode of said thirdcurrent control device to provide an operating bias by forming a controlelectrode to load electrode current path from the battery to groundwhich, in turn, renders said third current control device highlyconductive to energize saidthird indicating lamp; and

gate means coupled between the output of each of said first and secondcurrent control devices to the control electrode of said third currentcontrol device to disable said third current control device uponconduction of either said first or second current control device.

4. The voltage U regulator indicating circuit of claim 3 wherein saidfirst reference voltage circuit means is responsive to a below normalvoltage output of the dynamo-electric machine to energize said firstindicating lamp in response thereto;

said second reference voltage circuit means is responsive to an abovenormal voltage output of the dynamoelectric machine to energize saidsecond indicating lamp in response thereto;

and said third indicating lamp is energized by said switching circuit inresponse to a normal voltage output of the dynamoelectric machine.

5. The voltage regulator indicating circuit of claim 3 including fourthand fifth current control devices, each of said first and second currentcontrol devices being coupled to said fourth and fifth current controldevices respectively, a direct current coupled to the control electrodeof each of said fourth and fifth current control devices, and said firstand second reference voltage means being coupled to the controlelectrode of said fourth and fifth current control devices respectively,which are connected in circuit with said first and second currentcontrol devices.

6. The voltage regulator indicating circuit of claim 5 wherein saidfirst reference voltage means includes a zener diode connected incircuit in one polarity direction and said second reference voltagemeans includes a zener diode connected in circuit in the oppositepolarity direction..

7. The voltage regulator indicating circuit of claim 3 wherein said gatemeans includes a first diode direct current coupled between the outputof said first current control device and the control electrode of saidthird current control device, and a second diode direct current coupledbetween the output of said second current controlled device and thecontrol electrode of said third current control device.

l F l IIK

1. A voltage regulator indicating circuit for use in a vehicular systemwhich has a DC power source and a dynamoelectric machine for supplyingcharging current to the DC power source, comprising in combination:first and second indicators, voltage value responsive circuit meanshaving first and second inputs, said first input being coupled to the DCpower source and said second input to the output of said dynamoelectricmachine, said voltage value responsive circuit means comparing saidinputs and being coupled to said first indicator to energize the samewith said first and second inputs being substantially unequal, aswitching circuit coupled in circuit with the DC power supply, saidvoltage value responsive circuit means and said second indicator, saidswitching circuit energizing said second indicator with said voltages ofsaid first and second inputs of said voltage value circuit means beingsubstantially equal, and said switching circuit further being disabledwith said first and second inputs of said voltage value responsivecircuit means being substantially unequal.
 2. The voltage regulatorindicating circuit according to claim 1 including said voltage valueresponsive circuit energizing said first indicator over a firstpredetermined range of voltage differences between said first and secondinput voltages, a third indicator, second voltage value responsivecircuit means having a first and second inPut and an output, said firstinput being coupled to the DC power source and second input beingcoupled to said dynamoelectric machine, said second voltage valueresponsive circuit comparing said first and second inputs thereof andbeing coupled to said third indicator to energize the same in responseto said inputs being substantially unequal over a second predeterminedrange of voltage differences, said first and second voltage ranges beingdifferent, said second voltage value responsive circuit further beingcoupled to said switching circuit to disable the same over said secondrange of voltage differences.
 3. A voltage regulator indicating circuitto be connected to a battery charging circuit within an electricalsystem of a motor vehicle to indicate the operating conditions of thedynamoelectric machine used to charge the battery, comprising: a firstvoltage differential amplifier circuit having a first current controldevice which has a pair of load electrodes and a control electrode; afirst indicating lamp connected in circuit with the load electrodes ofsaid first current control device to be energized in response toconduction thereof; a first reference voltage means coupled to saidcontrol electrode of said first current control device, said firstreference voltage means arranged for connection to the battery chargingcircuit within the electrical system of the motor vehicle, said firstreference voltage means being rendered operative in response to a firstabnormal voltage output condition of the dynamoelectric machine withinthe electrical system of the motor vehicle, a second voltagedifferential amplifier circuit having a second current control devicewhich has a pair of load electrodes and a control electrode; a secondindicating lamp connected in circuit with the load electrodes of saidsecond current control device to be energized in response to theconduction thereof; a second reference voltage means coupled to saidcontrol electrode of said second current control device, said secondreference voltage means arranged for connection to the battery chargingcircuit within the electrical system of the motor vehicle, said secondreference voltage means being rendered operative in response to a secondabnormal voltage condition at the output of the dynamoelectric machinewithin the electrical system of the motor vehicle; a switching circuitincluding a third current control device having load electrodes and acontrol electrode, a third indicating lamp connected in circuit with theload electrodes of said third current control device to be energized inresponse to the conduction thereof to indicate a normal voltagecondition of the electrical system; resistance means connected to thecontrol electrode of said third current control device to provide anoperating bias by forming a control electrode to load electrode currentpath from the battery to ground which, in turn, renders said thirdcurrent control device highly conductive to energize said thirdindicating lamp; and gate means coupled between the output of each ofsaid first and second current control devices to the control electrodeof said third current control device to disable said third currentcontrol device upon conduction of either said first or second currentcontrol device.
 4. The voltage regulator indicating circuit of claim 3wherein said first reference voltage circuit means is responsive to abelow normal voltage output of the dynamo-electric machine to energizesaid first indicating lamp in response thereto; said second referencevoltage circuit means is responsive to an above normal voltage output ofthe dynamoelectric machine to energize said second indicating lamp inresponse thereto; and said third indicating lamp is energized by saidswitching circuit in response to a normal voltage output of thedynamoelectric machine.
 5. The voltage regulator indicating circuit ofclaim 3 including fourth and fifth current control devices, each of saidfirst and second current control devices being coupled to said fourthand fifth current control devices respectively, a direct current coupledto the control electrode of each of said fourth and fifth currentcontrol devices, and said first and second reference voltage means beingcoupled to the control electrode of said fourth and fifth currentcontrol devices respectively, which are connected in circuit with saidfirst and second current control devices.
 6. The voltage regulatorindicating circuit of claim 5 wherein said first reference voltage meansincludes a zener diode connected in circuit in one polarity directionand said second reference voltage means includes a zener diode connectedin circuit in the opposite polarity direction.
 7. The voltage regulatorindicating circuit of claim 3 wherein said gate means includes a firstdiode direct current coupled between the output of said first currentcontrol device and the control electrode of said third current controldevice, and a second diode direct current coupled between the output ofsaid second current controlled device and the control electrode of saidthird current control device.